1. Field of the Invention
The invention relates to vacuum gauges and, particularly, to an ionization vacuum gauge employed in situations in which the vacuum system is sensitive to temperature and/or light and/or in high vacuum systems.
2. Discussion of Related Art
Ionization vacuum gauges have been used for several years. The conventional ionization vacuum gauge includes a hot filament, an anode electrode surrounding the hot filament, and an ion collector surrounding the anode electrode. The anode electrode and the ion collector are coaxial relative to the hot filament. In operation, electrons emit from the hot filament, travel toward and through the anode electrode and eventually are collected by the anode electrode. In their travel, electrons collide with the molecules and atoms of gas and produce ions, and eventually ions are collected by the ion collector. The pressure of the vacuum system can be calculated by the formula P=(1/k) (Iion/Ielectron), wherein k is a constant with the unit of 1/torr and is characteristic of a particular gauge geometry and electrical parameters, Iion is a current of the ion collector, and Ielectron is a current of the anode electrode.
However, the conventional ionization vacuum gauge requires several watts of electrical power supply to the hot filament, the hot filament dissipates heat and light in the vacuum system, and consequently the conventional ionization vacuum gauge is unsuitable for use in a vacuum system sensitive to heat and/or light. Furthermore, the high temperature of the hot filament can cause evaporation, and thus the conventional ionization vacuum gauge tends to be unsuitable for high vacuum systems.
What is needed, therefore, is an ionization vacuum gauge that is suitable for use vacuum systems that are sensitive to temperature and/or light and/or that requires extremely high vacuum levels.